Wheel speed sensor

ABSTRACT

A system for mounting a wheel speed sensor mechanism including a magnetic sensor and a rotor on a vehicle axle and wheel to assure disposition of the sensor and rotor in precisely predetermined relation during operation and upon initial installation and reinstallation of the wheel.

United States Patent [191 Cumming NOV. 13, 1973 WHEEL SPEED SENSOR [75]Inventor: James C. Cumming, Pleasant Ridge,

211 App]. No.: 249,659

3,500,091 3/1970 Jones 310/168 Primary Examiner-D. F. Duggan Att0meyJohnR. Bronaugh et al.

[5 7] ABSTRACT [52] US. Cl. 310/168 A system for mounting a wheel speedsensor mecha- [51] Int. Cl. H02k 19/24 1 nism including a magneticsensor and a rotor on a ve- [58] Field of Search 310/168, 68, 67, hicleaxle and wheel to assure disposition of the sensor 310/154, I55 androtor in precisely predetermined relation during operation and uponinitial installation and reinstalla- [56] References Cited tion of thewheel.

UNITED STATES PATENTS 3,482,129 12/1969 Riordan 310/168 X 4 Claims, 4Drawing Figures 58 3O a4 94 6O 3 es 5e 2e PATENIEDnuv 13 1913 3372.549

SHEET 1 CF 2 PATENTEI] NOV 13 I973 SHEET 2 BF 2 FIG. 2

FIG. 3

WHEEL SPEED SENSOR BACKGROUND OF THE INVENTION Most modern anti-skidcontrol systems function in response to electrical signals indicative ofthe angular velocity of one or more of the vehicle wheels. Generallythese signals are derived from an electromagnetic sensor including amagnet carried by a stationary portion of the vehicle such as the axlehousing, and a toothed or notched ring rotatable with the wheel oppositethe magnet. As the teeth or notches of the ring pass the magnetic sensordevice the resulting variations in flux generate a signal, the frequencyof which is a function of the angular velocity of the wheel.

To produce the required accuracy of the velocity signal the sensor andring must be precisely located with respect to each other and mustremain in a preselected relationship even after extended operation inwhich the components are subjected to road shocks and constantvibration. Further, the continued effectiveness of the velocity sensingunit requires that it be fully protected against dirt, mechanical damageand heat.

It is also essential that installation techniques be adaptable to massproduction methods and minimize the requirement for highly skilledtechnicians and elaborate installation techniques. The. mounting of thesensor units must also be such that upon reinstallation of a wheel afterremoval for repair, the parts will automatically be restored to theiroriginal operating position.

Prior proposals for mounting the velocity sensor elements have ingeneral failed to satisfy one or more of these criteria and in generalhave achieved a degree of accuracy only at a substantial cost penalty.

SUMMARY OF THE INVENTION It is the principal purpose and object of thepresent invention to provide improved systems for mounting THE DRAWINGSFIG. 1 is a fragmentary section showing a typical wheel speed sensormounting system in accordance with the present invention;

FIG. 2 is a slightly enlarged fragmentary view showing a modified wheelspeed sensor mounting system;

F103 is a plan view of one of the sensor components removed from theassembly; and

FIG. 4 is a side elevation of the components shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For present purposes theinvention will be disclosed as applied to a non-steerable vehicle axle,particularly vehiclewheel speed sensor devices of the type described,the mounting system assuring that the rotating and stationary componentsof the sensor device will be positioned in precisely predeterminedrelationship at initial installation and upon reinstallation of thewheel and will remain in proper operating relationship throughout anextended period of service.

It is a further object of the present invention to provide improvedsystems for mounting wheel speed sensor devices which facilitate lowcost rapid installation of the sensor components and which assure thatthe sensor components will be maintained in proper relationshipautomatically upon removal and reinstallation of the wheel.

It is also an object of the present invention to provide improvedsystems for mounting wheel speed sensors which protect the sensorcomponents from dirt and other foreign matter and from mechanical damageand heat.

Additional objects and advantages will become apparent as thedescription proceeds in connection with accompanying drawings.

In attaining these objects and other objects the present inventionprovides a pair of accurately formed annular mounting surfaces, one onthe axle and one on the wheel hub, the annular mounting surfaces beingdisposed in precisely predetermined relation when the wheel hub isinstalled on the axle.

The rotating and stationary components of the sensor mechanism areassembled to the annular mounting suran axle designed for heavy dutyuse, such as a rear axle of a truck. As used herein the term *axle" isintended to refer to any component on which a wheel hub is mounted andincludes components sometimes called spindles or axle housings.

Typically, the axle 20 is of hollow tubular construction to accommodatean axle shaft which may be installed if the wheels are to be driven. Atits outer end the axle 20 is provided with a pair of bearing seats 22and 24 for inner and outer bearing assemblies 26 and 28 upon which thewheel hub 30 is supported. Upon installation of the wheel hub the innerbearing 26 is moved into position against an accurately located radialshoulder 32 on the axle 20 and the parts are locked in this position bya lock nut assembly 34 threaded onto the outer end of the axle 20 andbearing against the inner race of the outer bearing assembly 28 toimpart a predetermined preload to the two bearing assemblies 26 and 28.Y

The brake drum 36 is secured by a plurality of bolts 38 to a radialflange 40 on the wheel hub 30, the flange also carrying a plurality ofwheel mounting studs 42 circumferentially spaced from the bolts 38. Thebrake assembly, which is conventional, includes brake shoes 44 carryinglinings .46 and a brake operating mechanism, not shown, carried by aspider or backing plate, a portion of which is shown at 48 mounted on aradial flange 50 formed integrally with the axle 20.

Lubricant for the bearing assemblies 26 and 28 is carried in a cavity52, the outer end of which is sealed by means not shown, the inner endof which is sealed by seal members 54 and 56 carried by the wheel huband axle, respectively. The structure thus far described in conventionaland per se forms no part of the present invention.

The wheel speed sensor assembly comprises two principal components,steel ring 58 carried by the wheel hub 30, the ring having a pluralityof equally circumferentially spaced notches or teeth 60 on its inboardface and the second element being a magnetic sensor unit 62 carried bythe axle 20.

In a typical case the ring 58 will have an CD. of 8.5 inches and will beprovided with equally spaced teeth 60 having a radial length ofapproximately 0.75 inches and a depth of approximately 0.125 inches.

The magnetic sensor unit 62, shown separately in FIGS. 3 and 4, is ofarcuate configuration being formed on the same radius as the ring member58 and in a typical case having a radial width of approximately 1 inch.The unit comprises a magnet assembly which may be of the E-core typehaving three exposed poles 66 suitably mounted in a plastic body portion68 and a second portion 70 containing electric components (not shown)which convert to signals generated by the magnet to the proper form foruse in the brake control system. The leads to the power supply for thesensor unit 62 as well as for the output signal are contained in thecable 72 leading into one end of the unit.

Proper operation of the sensor unit 62 can be obtained only if it isprecise located with respect to the ring 58. The sensor 62 and the ring58 must be essentially concentric. More important, the gap between theface of the ring 58 and the poles 66 must be held within close limits asthe ring 58 rotates. To avoid runout or variations in gap width inoperation, the axis of rotation .of the ring 58 must be substantiallyexactly perpendicubearing seats 22 and 24 for the wheel hub 30. The

mounting member 78 also has a cylindrical shield portion 84 surroundingthe outer surface of the sensor assembly 62 and the ring 58 andperforming the dual function of protecting the components against theentry of dirt and foreign objects and shielding the sensor assembly 62from the heat generated during application of the brakes.

The sensor unit 62 is installed by first bolting it to the mountingmember 78. Thissub-assembly is then press fitted onto the axle mountingsurface 82. Preferably the installation of the mounting member 78 iseffected with a tool which has one radial surface adapted to bearagainst the inner face of the radial portion 76 of the member78 and asecond radial face adapted to rear against the shoulder 32 when themounting member 78 reaches the proper axial position.

Similarly, the member 58 is press fitted onto an annular mountingsurface 86 formed on the wheel hub 30, the surface 86 being machined torender it concentric with the axis of the hub 30. Preferably the ring 58is installed by the use of a tool having a first radial face adapted toengage the ends of the teeth 60 and a second radial face adapted toengage the annular shoulder 88 which locates the outer race of bearingassembly 26.

When the wheel hub 30 is subsequently installed on the axle as shown inFIG. 1 and the nut assembly 34 is tightened to preload the precisionbearings 26 and 28, the ring 58 and sensor'asse'mbly 62 will beautomatically disposed in proper relationship which in a typical caseprovides a gap of 0.040 inches between the faces of the teeth 60 on thering 58 and the faces of the pole pieces 66 on the sensor unit 62.Problems of runout, that is, variations in gap width as the ring 58rotates are virtually eliminated.

The mounting member 78 effectively shields the sensor unit 62 againstheat and mechanical damage, the latter function being augmented by theslinger ring secured to the wheel hub flange 40. The slinger ring alsodirects excess oil which may leak past the seal 56 to one or more drainopenings 92 extending through the flange 40.

Removal and replacement of the wheel hub 30 may be effected using onlytechniques normally associated with such an operation. Uponreinstallation of the wheel hub the ring 58 and the sensor 62 will beautomatically correctly repositioned.

The modification shown in FIG. 2 is essentially the same as that shownin FIG. 1 except that the outer annular portion 84 of the sensor supportmember 78 is axially extended in an outboard direction and carries aseal member 94 cooperating with a slinger ring 90 to further seal thespace in which the ring and the sensor element operate and protect theseelements from mechanical damage.

I claim:

1. In combination with an elongate vehicle axle and a wheel rotatablymounted on said axle, a wheel speed sensor assembly comprising a ringmember having discontinuities on a radial face thereof, said ring memberbeing secured by a press fit about a portion of said wheel for rotationtherewith with said discontinuities facing axially inwardly, a magneticsensor assembly, a mounting member for said sensor assembly, saidmounting member having an axially outwardly facing radial facesupporting said sensor assembly and an axially extending annular portionsecured by a press fit onto said axle, said sensor assembly and saidring being disposed in a predetermined relation with a predeterminedspacing betwen said sensor and said discontinuities on said ring.

2. The assembly according to claim 1, together with a stationary shieldrigid with said mounting member and extending around the radially outersurface of said sensor assembly.

3. The assembly according to claim 2 together with an annular shieldadapted to be carried by said wheel and extending axially intooverlapping relation with said stationary shield.

4. The assembly according to claim 3, together with a seal extendingbetween the overlapping portions of said annular shield and saidstationary shield.

1. In combination with an elongate vehicle axle and a wheel rotatably mounted on said axle, a wheel speed sensor assembly comprising a ring member having discontinuities on a radial face thereof, said ring member being secured by a press fit about a portion of said wheel for rotation therewith with said discontinuities facing axIally inwardly, a magnetic sensor assembly, a mounting member for said sensor assembly, said mounting member having an axially outwardly facing radial face supporting said sensor assembly and an axially extending annular portion secured by a press fit onto said axle, said sensor assembly and said ring being disposed in a predetermined relation with a predetermined spacing betwen said sensor and said discontinuities on said ring.
 2. The assembly according to claim 1, together with a stationary shield rigid with said mounting member and extending around the radially outer surface of said sensor assembly.
 3. The assembly according to claim 2 together with an annular shield adapted to be carried by said wheel and extending axially into overlapping relation with said stationary shield.
 4. The assembly according to claim 3, together with a seal extending between the overlapping portions of said annular shield and said stationary shield. 